Typical examples of container-handling machine used in the food-product bottling industry are blowing machines, filling machines and/or labelling machines.
Container-handling machines substantially comprise a carousel, which is rotatable along an axis and supports a plurality of container-holding plates.
Furthermore, container-handling machines could also comprise an encoder in order to detect the angular position of the carousel. The encoder is normally connected to a shaft of the carousel rotating about the axis by a transmission group, i.e. belt, pulley or gear.
The presence of the transmission group between the shaft of carousel and the encoder inevitably causes mechanical plays which may penalize the accuracy of the measure carried out by the encoder.
Furthermore, due to the presence of the transmission group, encoder is mounted quite remote from the shaft. Accordingly, the vibrations caused by operation of container-handling machine may further penalize the accuracy of the measure carried out by the encoder.
Known container-handling machine may also comprise a so-called “slip-ring” in order to transfer power and/or control signals from a static supply unit and a rotatable component, as for example the shaft of the carousel. More precisely, slip-ring may transfer electrical, hydraulic or pneumatic power or control signals.
Very briefly, slip-ring comprises a conductive ring mounted on the rotatable component and insulated from it, and a plurality of fixed brushes in contact with the conductive ring.
Due to the lack of space, it could be very difficult to fix the encoder to the shaft of the carousel when container-handling machine comprises slip-ring.
A need is felt within the industry to accurately detect the angular position of the shaft of the carousel of a container-handling machine comprising a slip-ring.
Furthermore, a need is felt within the industry to meet the above requirement without changing the design of the main components of the container-handling machine, for instance the carousel.
The above-mentioned needs are especially felt when the container-handling machine is a labelling machine typically used to apply labels onto containers.
In this case, as a matter of fact, there is a connection between the shaft and the supporting elements of respective container, and the angle and the speed of the supporting elements are strongly higher than the angle and the speed of the shaft.
Therefore, even very small errors in the measure of the position of the shaft may lead to considerable errors in the final position of the label onto the container.
In more general terms and regardless of the technical sector, a need is felt to accurately detect the angular position of a carousel of a rotary machine comprising a slip-ring.